This invention relates to a distributor type fuel injection pump for supplying fuel to an engine, especially a distributor type fuel injection pump (an inner cam system fuel injection pump) in which plungers are provided slid ably in radial direction in a rotor rotating synchronously with an engine, and the plungers are made to reciprocate by moving on a cam surface of a cam ring to vary the volume of a compression space formed in the rotor.
An inner cam system distributor type fuel injection pump is, for instance, as shown in Unexamined Patent Publication No. S59-119056, Unexamined Patent Publication No. S60-79152, Unexamined Patent Publication No. H3-175143 and so on, constructed such that an inner cam (a cam ring) is located around a fuel distributing rotation member (a rotor), compressing plungers are engaged on a cam surface formed inside of the inner cam via a rolling member, etc., and the compressing plungers are made to reciprocate in radial directions of the fuel distributing rotation member. The fuel distributing rotation member is provided with a pump chamber (a compression space) whose volume is varied by the compressing plungers, an intake hole for inhaling fuel into the pump chamber in an intake process, a distributing port for delivering fuel compressed in the pump chamber in a delivery process, and an over-flow port for cutting off delivery of fuel. A ring-shaped member (a control sleeve) is fitted outside of the fuel distributing rotation member so as to cover the over-flow port, and cut-off timing in the delivery process is varied by moving the ring-shaped member in the axial direction, so that injection quantity may be varied.
A system of power transmission for supplying rotation power to the rotation member of this injection pump is constituted such that drive pulleys mounted on a crank shaft of the engine, a cam shaft for an intake/discharge valve, and a drive shaft of the injection pump are connected by a timing belt, the timing belt is given a specific tension to reliably supply drive power of the engine to the drive shaft of the injection pump and to maintain timing of operation between pistons of the engine and the intake/discharge valve in good condition.
By the way, in the fuel injection pump, for increasing performance of injection, a small tolerance is required for a clearance between the rotation member and the members with respect to which the rotation member slides. In lubrication in this sliding portion, fuel which is to be compressed is used as a lubricating oil, so that fuel with impurities sufficiently removed is used. Though this is managed sufficiently, if fine foreign matter flows into the fuel injection and enters into the sliding portion of the rotation member, the sliding portion of the rotation member is damaged, so that smooth sliding is lost and then the rotation member is seized at the sliding portion and, as a result, there is a problem that the rotation movement of the rotation member is restrained.
If the rotation member or the member with respect to which the rotation member slides is deformed in some manner, a clearance of the contacting sliding portion set in advance is not maintained and, as a result, it may possibly seize in a similar manner.
Though thus seizure of the rotation member does not usually occur, if anything should happen, the engine stops because fuel injection to the engine is terminated, but the engine does not stop simultaneously to seizing (sticking) of the rotation shaft in the injection pump. Although the drive shaft of the injection pump is locked up (seized), the drive force is transmitted from the crank shaft to the timing belt to cause jumping of the teeth of the timing belt. Thus, the phase between the crank shaft and the cam shaft for the intake/discharge valve deviates and the timing of operation between the pistons of the engine and the intake/discharge valve deviates so that they come into collision with each other and, as a result, it may be possible to cause considerable damage to engine. If this should occur, not only the injection pump be repaired but also the engine itself must be repaired.